Recently, portable terminals such as smartphones equipped with a digitizer function have released and become popular. A digitizer using an electronic pen can draw a line of about 0.7 mm thick which is more elaborate than a capacitive touch panel which recognizes a line of 3-4 mm thick. Therefore, the digitizer using an electronic pen can easily perform a fine operation.
The digitizer function is also applied to a large-screen tablet personal computer (PC) or the like that employs a large display, as well as a small portable terminal device such as a smart phone.
In order to employ the digitizer function using electromagnetic induction for a portable terminal, a magnetic field shielding sheet for shielding an electromagnetic field generated from various parts of a portable terminal device body is inserted between a digitizer panel and a main circuit board.
An electromagnetic wave shielding member using a conventional ribbon, as disclosed in Korean Patent Publication No. 10-0460297 (on Nov. 26, 2004), includes: a metal ribbon composed of any one metal or alloy selected from the group consisting of Ni—Fe—Mo, Fe—Si and mu-metal and whose relative magnetic permeability is 1000 or more, in which the thickness of the metal ribbon is between 1 μm and 900 μm, and the width of the metal ribbon is in the range of from 1 mm to 90 mm; and an adhesive layer formed on at least one side of the metal ribbon.
Such a conventional electromagnetic wave shielding member may cause radiation to the opposite side of the metal ribbon which a magnetic field enters, in which the magnetic field passes through and along the plane of the metal ribbon when the magnetic field is applied from outside along the side of the metal ribbon in the case that the metal ribbon is in a flat plate form.
Further, when the electronic pen function is added to a portable terminal device, a digitizer panel is attached to the body of the portable terminal device body. In this case, a magnetic field shielding sheet is provided to avoid affecting the digitizer function by a magnetic field generated by various parts built in the portable terminal device body.
A frame for reinforcing an overall strength of the portable terminal device body and supporting various parts is provided in the portable terminal device. A lightweight and high-intensity magnesium frame is mainly used therefor.
However, in the case of using the magnesium frame, the digitizer is influenced by a magnesium material of the magnesium frame, to thereby cause a problem that the digitizer function is reduced.